Recreation at the beach typically includes both land and water activities, and can include the use of diverse water and land craft.
A wide variety of recreational watercraft are known. For example, watercraft comprising a hull and a pair of paddle wheels are taught in U.S. Pat. No. 6,247,981 B1. Attempts have been made to adapt recreational watercraft for use on land, or conversely to adapt recreational land vehicles for use on water.
U.S. Patent Publn. No. U.S. 2004/0087224 A1 teaches an aquatic vehicle having a frame suspended between a pair of large flotation wheels equipped with paddles mounted to the sides of the wheels. The wheels are pedal-driven, and the vehicle is capable of being propelled across level ground or over water.
U.S. Pat. No. 3,595,199 discloses an engine-driven boat hull comprising wheels for propulsion on land and an engine-driven, water jet propulsion system for propulsion on water. Similarly, U.S. Pat. No. 4,473,358 teaches a hulled watercraft equipped with propulsion wheels capable of producing forward thrust and also of exerting a downward pressure upon the water to lift the hull and thereby reduce hull drag. The axles of this vehicle may further comprise tires for propulsion on land.
Bicycles that are adaptable for use on water by the attachment of pontoons are described in U.S. Pat. Nos. 6,050,864 and 4,395,237.
However, each one of these references suffers from one or more of the following disadvantages: the wheels may be overly large, making land travel difficult except over smooth, hard, level surfaces; designs in which the frame is suspended from only one pair of wheels may be unstable when entry of the vehicle is attempted from water; paddles or other aquatic drive means that are positioned on the sides of a wheel or paddle in order to permit land travel may be inefficient for propulsion in water; the weight and/or complexity of the design may require a motor; and time-consuming addition or removal of flotation devices may be required when transitioning between water and land.
The drive means of an amphibious vehicle must be efficient if the amphibious craft is to be satisfying, fun, and practical. It is therefore desirable to minimize drag and other mechanical losses. For example: losses in the drive train should be minimized; the use of fixed flotation devices such as hulls or pontoons, which produce substantial drag in water, should be avoided; wheels should be of a suitable size for maneuverability on land; and the use rudders, which also produce substantial drag in water, should be avoided.
Attempt to address issues related to efficient drive means for amphibious vehicles can be found, for example, in U.S. Pat. No. 3,628,493, which discloses an aquatic impellor wheel with impact surfaces capable of producing upward thrust when rotated in water, and U.S. Pat. No. 5,058,643, which discloses a tire comprising tread blocks adapted to provide both propulsion on water and traction on land. However, these approaches suffer from one or more of the following disadvantages: the power required to produce significant upward thrust on water is high; and a tire tread provides only limited traction in water.
For the foregoing reasons, there is a need for a lightweight, buoyant, and maneuverable amphibious vehicle capable of efficient propulsion on both land and water, and which is capable of moving between water and land without the need for mechanical adjustment. All this and more will become apparent to one of ordinary skill upon reading the disclosure, figures, and claims appended hereto.